This invention relates to semiconductor laser with light guide wherein a light guide part is coupled to a light output part of the semiconductor laser.
Semiconductor lasers are useful as light sources for integrated optical circuits. Matching between the light guides and end parts of laser active regions, namely the Fabry-Perot cavities, are important in the proper operation of the semiconductor laser. In order to attain satisfactory matching, it is desirable to make the semiconductor laser and the light guides in a united structure.
Such united structure of the semiconductor laser and light guides is described in an article entitled "Integrated GaAs-AlGaAs double heterostructure laser" by C. E. Hurwitz etal in "Applied Physics Letters", vol. 27, No. 4,15 August 1975, pages 241 - 243. In this article, as shown in FIG. 1 of a sectional view, a semiconductor laser comprises a laser part 10 and a light guide part 11 on a single wafer. The laser part is made by sequential epitaxial growths on a substrate 5 of n-type GaAs, of a first layer 1 of n-type Ga.sub.0.7 Al.sub.0.3 As, a second layer 2, i.e., an active region 2 of p-type GaAs, a third layer 3 of p-type Ga.sub.0.7 Al.sub.0.3 As and a fourth layer 4 of p-type GaAs, in sequence and then attaching electrodes 6 and 7. The light guide parts 11 is made by forming n-type GaAs of low impurity concentration in mesa-etched hollow parts of the laser part 10. The laser part and the light guide parts 11 are isolated from each other by an insulation films 8, 8 such as SiO.sub.2 inbetween.
In such semiconductor laser of the prior art, the light guide parts are several times thicker than the active region 2, and accordingly, the lasing light from the active region 2 diverges into such wide angle of several tens of degrees, thereby making convergence of the lasing light difficult.